1. Field of the Invention
The present invention relates to an apparatus and a method for providing a video telephony service. More particularly, the present invention relates to the provision of a high quality video telephony service by supporting multiple video formats for a video telephony service between mobile communication terminals.
2. Description of the Related Art
A Video Telephony (VT) service in a current third generation (3G) network follows the 3G-324M international standard specification. The maximum capacities of video, voice and data, recommended in the international standard specification, depend on the capacity of a data transmission apparatus. However, the maximum capacity of a Circuit Switched Domain (CSD) network for a video telephony service in the 3G network is 64 kilo bits per second (64 kbps).
That is, the video data rate, voice data rate and rate for data communication in the CSD network are limited to 64 kbps each. Normally, the video data rate is 48˜52 kbps, the voice data rate is 4˜12 kbps, and the rate for date communication is 2 kbps.
A video telephony service under the 3G-324M protocol is designed for data transmission between mobile communication terminals. Accordingly, the video telephony service by the 3G-324M protocol should guarantee an inter-compatibility between service providers.
Therefore, the video telephony service under the 3G-324M protocol is adopted as the standard specification and a video telephony service under the 3G-324M protocol is used by most service providers for a simple and precise video telephony service between users.
Because the video telephony service by the 3G-324M protocol is for data transmission between mobile communication terminals, the video telephony service by the 3G-324M protocol has a limited resource capacity in maximum transmission and reception and the service providers have a limitation in an operation of the 3G network.
End users usually receive a poor quality image during a video telephony service due to the limitations listed above so that the video telephony service is unpopular. Especially, due to the limited communication capacity, a Quarter Common Intermediate Format (QCIF) (176*144 resolution) is used as a formulaic video format in all 3G mobile communication terminals.
However, the small sized QCIF format cannot provide sufficient quality to users having mobile communication terminals with performance enhancements such as larger Liquid Crystal Displays (LCD) or faster processors. Also, the video telephony service under the 3G-324M protocol uses common standard video formats to guarantee inter-compatibility between the service providers. However, appropriate video formats corresponding to the physical performance enhancement in the mobile communication terminal are not provided.
When an encoding procedure is used in the video telephony service, original video data is damaged and it is impossible to decode encoded video data equivalent to the original video data. Thus, users receive a poor quality video telephony service.
When a peer mobile communication terminal does not have an LCD panel which cannot satisfy a QCIF resolution, an image processing for adjusting the QCIF resolution is required. According to the adjusting of the QCIF resolution, the decoded video data is damaged again.
Therefore, there is a need to provide an apparatus and a method employing an enhancement in the 3G-324M protocol, which only supports video data with low resolution, to address the limitations of the video telephony service.